It has been shown that captopril, an angiotensin converting enzyme (ACE) inhibitor decreased the development of experimental atherosclerosis in monkeys fed cholesterol (Aberg, G. and Ferrer, P. "Effects of Captopril on Atherosclerosis in Cynomolgus Monkeys," J. Cardiovascular Pharmacology, 15 (suppl.5), S65-S72, 1990), and in the genetic hyperlipidemic Watanabe rabbit (Chobanian, A. V. et al, "Antiatherogenic Effect of Captopril in the Watanabe Heritable Hyperlipidemic Rabbit," Hypertension, 15, 327-331, 1990). It is also known that captopril and cilazapril retarded the proliferation of intimal smooth muscle cells after denuding the carotid artery of rats with a balloom catheter (Powell, J. S. et al, "Inhibitors of Angiotensin-Converting Enzyme Prevent Myointimal Proliferation After Vascular Injury," Science 245, 186-188, 1989). However the effect of ACE inhibitors on the initial cellular events of atherosclerosis remain unkown.
In early atherosclerosis, the monocyte/macrophage is a key player. Hypercholestrolemia promotes the adhesion of blood-borne monocytes to the luminal surface of arteries, and then these leukocytes migrate into the intima. As tissue macrophages, they phagocytose modified LDL particles and transform into foam cells. Foam cells accumulate in the intima to form fatty streaks and they are also present in mature atherosclerotic plaques (Ross, R., "The Pathogenesis of Atherosclerosis--an Update," N. Engl. J. Med., 314, 488-500, 1986; Munro, J. M. and Cotran, R. S., "Biology of Disease. The Pathogenesis of Atherosclerosis: Atherogenesis and Inflammation," Lab. Invest., 58, 249-261, 1988; Steinberg, D. et al, "Beyond Cholesterol. Modifications of Low-Density Lipoprotein that Increases its Atherogenicity," N. Engl. J. Med., 320, 915-924, 1989).
European Patent Application 0219782 to Scholkens (Hoechst) discloses the treatment of atherosclerosis, thrombosis and/or peripheral vascular disease in mammals using an angiotensin converting enzyme (ACE) inhibitor or its physiologically tolerable salts. It further discloses that because ACE is predominantly localized in the luminal plasma membrane of the endothelial cell, ACE inhibitors can interfere in platelet-endothelium interaction. In addition, Scholkens discloses that ACE inhibition potentiates the action of bradykinin (a strong stimulator of prostacyclin release from endothelial cells) by inhibiting its degradation and ACE inhibitors, consequently, have an inhibitory effect on platelet aggregation.
Zorn, J. et al, "Prevention of Arteriosclerotic Lesions with Calcium Antagonists or Captopril in Different Rat Hypertension Models," J. Cardiovasc. Pharmacol. Vol. 12 (Suppl 6), 1988, discloses beneficial effects in mesenteric arteries atherosclerosis with captopril in spontaneous hypertensive Okamoto rats (SHRs), but not in salt-sensitive Dahl rats.
Someya, N. et al, "Suppressive Effect of Captopril on Platelet Aggregation in Essential Hypertension," J. Cardiovasc. Pharmacol. 6:840-843, 1984, discloses at page 840 that "hypertension is closely related to the genesis and progress of atherosclerosis," and that "platelet function plays an important role in atherosclerosis, with platelet dysfunction demonstrable in several vascular diseases. It has been reported that platelet aggregation is increased in hypertensives . . . ." At page 842, it is indicated that the "data demonstrated the inhibition of platelet aggregation in vivo after administration of captopril to hypertensive subjects . . . ." At page 843, it is indicated that "platelet aggregability is greater in hypertensives than in normotensives . . . platelet abnormalities may be a risk factor in atherosclerosis . . . . If captopril possesses an antiplate aggregability effect in addition to its hypotensive effect, it may be very useful for the prevention of atherosclerosis and thrombotic diseases associated with hypertension."
Mizuno, K. et al "The effects of the angiotensin I-converting enzyme inhibitor, captopril, on serum lipoperoxides level and the renin-angiotensinaldosterone and kallikrein-kinin systems in hypertensive patients," Nippon Naibunpi Gakkai Zasshi, Feb. 20, 1984, discloses that captopril is a beneficial antihypertensive agent for preventing serum lipoperoxides concentration (LPX)-induced atherosclerosis in hypertensive patients.
Mizuno, K. et al "Acute effects of captopril on serum lipid peroxides level in hypertensive patients," Tohoku J. Exp. Med., May, 1984, 143(1) p. 127-8, suggests that inhibition of angiotensin-converting enzyme by captopril offers a possible therapeutic approach to the treatment of atherosclerosis complicated with hypertension.
The role of the renin-angiotensin system in atherosclerosis is not clear. Campbell-Boswell Robertson, Exp. and Mol. Pathol. 35:265 (1981) reported that angiotensin II stimulated proliferation of isolated human vascular smooth muscle cells while Geisterfer et al, Circ. Res. 62: 749-756 (1988) showed no proliferation (but stimulation of growth) of isolated rat vascular smooth muscle cells.
Overturf, M. et al, Atherosclerosis, 59:383-399, 1986, discloses that studies with ACE inhibitors in cholesterol fed rabbits show no significant effects in the development of atherosclerosis.
Cecil, Textbook of Medicine, 16 Ed., pp 239 to 241, indicates at page 240 that blood pressure is an accelerator of atherosclerosis.
U.S. Pat. Nos. 4,046,889 and 4,105,776 to Ondetti et al disclose proline derivatives, including captopril, which are angiotensin converting enzyme (ACE) inhibitors useful for treating hypertension.
U.S. Pat. No. 4,337,201 to Petrillo discloses phosphinylalkanoyl substituted prolines, including fosinopril, which are ACE inhibitors useful for treating hypertension.
U.S. Pat. No. 4,374,829 discloses carboxyalkyl dipeptide derivatives, including enalapril, which are ACE inhibitors useful for treating hypertension.
U.S. Pat. No. 4,452,790 to Karanewsky et al discloses phosphonate substituted amino or imino acids and salts thereof and covers (S)-1-[6-amino-2-[[hydroxy(4-phenylbutyl)phosphinyl]oxy-1-oxohexyl]-L-prol ine (SQ 29,852, ceronapril). These compounds are ACE inhibitors useful in treating hypertension.